The present invention relates to locking threaded fasteners, and more particularly to lock nuts that include a spring coil or band as a locking element.
Lock nuts can include a spring coil or band as a locking element. Typically, the locking element includes one end bent radially outwardly and anchored with respect to the nut, for example, with the bent end fitted within a slot in the nut. Under loosening torque, the nut creates a tension load on the locking element, which causes the element to tighten its grip to prevent unintended relative rotation (i.e. loosening). The opposite force, compression, is created on the locking element during tightening (i.e. installation), which causes the locking element to loosen its grip so that there is relatively low installation torque.
This locking system typically requires special tools or other means to enable removal of the nut. However, a number of lock nuts do not require special tools, for example, as disclosed in U.S. Pat. No. 8,021,093 issued Sep. 20, 2011 to Campau; U.S. application Ser. No. 12/880,580 filed Sep. 13, 2010 by Campau; and U.S. application Ser. No. 13/113,357 filed May 23, 2011 by Campau. The lock nut disclosed in the '357 application includes a locking element that slips at a controlled removal torque.
Unfortunately, the through slots of the noted lock nuts permit dirt, grease, and other contaminants to enter the lock nut through the slot. These contaminants can increase or decrease the locking force of the lock spring, depending on the contaminant. Such a change can make the lock nut unsuited for its intended application.